Technical Field
Preserving & Waterproofing Cellulose Materials
This invention relates to preserving and waterproofing of articles and materials such as
wood, drywall, paper, other wood products, fabric, and concrete, to methods for producing
hydrophobic materials and products, and particularly to the preparation and use of alkyl
ketene dimers (AKD) and silane formulations for such purposes.
Prior Art — Challenge 01
AKD Emulsion Instability
Alkyl Ketene Dimer (AKD) has been used in the paper industry since the 1950s to impart
water repellency by chemically reacting with cellulose fibers. However, AKD emulsions have
a limited shelf life of only 30–60 days because AKD
reacts with water, forming products that no longer react with cellulose. Treatments become
less effective in a relatively short time.
Prior Art — Challenge 02
Oligomer Formation in Silane Solutions
Prior art requires alkylalkoxysilanes to be hydrolyzed and diluted in an aqueous medium.
The resulting alkylhydroxysilanes have a shelf life of only hours
to days due to self-condensation forming oligomers. This limits concentrations to
<1% and introduces lengthy preparation time, increased storage requirements, and additional
operating personnel—making it restrictive at industrial scale.
The BEST Solution™
Surprisingly Stable AKD + Silane Emulsion
Combining alkylalkoxysilanes and AKD with water and an emulsifier produces a
surprisingly stable emulsion. This combination is performed at
mild temperatures since AKD melts at relatively low temperatures (40–60°C). Once liquified,
AKD readily dissolves into silanes. Emulsification is effectively performed using a sheer blender.
The resulting emulsion is stable for months. The silanes tend to associate
with AKD more than with water, inhibiting the formation of oligomers. Synergistically, the silanes also
inhibit the degradation of AKD by limiting the hydrolysis reaction of AKD with water. Treatment with
the alkylalkoxysilane/AKD emulsion requires a significantly smaller volume
to impart hydrophobicity compared to prior art methodology.
